<div class="panel panel-primary">
  <div class="panel-heading">模板内部定义局部变量的写法</div>
  <div class="panel-body">
    <input #heroInput>
    <p>{{heroInput.value}}</p>
    <button class="btn btn-success" (click) = 'sayHello(heroInput.value)'>sayHello</button>
  </div>
</div>